Nitride semiconductor structure and semiconductor light emitting device including the same

ABSTRACT

A nitride semiconductor structure and a semiconductor light emitting device are revealed. The semiconductor light emitting device includes a substrate disposed with a first type doped semiconductor layer and a second type doped semiconductor layer. A light emitting layer is disposed between the first type doped semiconductor layer and the second type doped semiconductor layer. The second type doped semiconductor layer is doped with a second type dopant at a concentration larger than 5×1019 cm−3 while a thickness of the second type doped semiconductor layer is smaller than 30 nm. Thereby the semiconductor light emitting device provides a better light emitting efficiency.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Reissue Application of U.S. Pat. No. 9,147,800issued on Sep. 29, 2015, application Ser. No. 13/963,127, filed on Aug.9, 2013, which claims the priority benefit of Taiwan application No.101143153, filed on Nov. 19, 2012. The entirety of each of theabove-mentioned patent applications is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a nitride semiconductor structure and asemiconductor light emitting device, especially to a nitridesemiconductor structure and a semiconductor light emitting deviceincluding a second type doped semiconductor layer with a high dopantconcentration (larger than 5×10¹⁹ cm⁻³) and a small thickness (smallerthan 30 nm) to improve a light-extraction efficiency and make thesemiconductor light emitting device have a better light emittingefficiency.

2. Description of Related Art

Generally, a nitride light emitting diode is produced by forming abuffer layer on a substrate first. Then a n-type semiconductor layer, alight emitting layer and a p-type semiconductor layer are formed on thebuffer layer in turn by epitaxial growth. Next use photolithography andetching processes to remove a part of the p-type semiconductor layer anda part of the light emitting layer until a part of the n-typesemiconductor layer is exposed. Later a n-type electrode and a p-typeelectrode are respectively formed on the exposed n-type semiconductorlayer and the p-type semiconductor layer. Thus a light emitting diodedevice is produced. The light emitting layer has a multiple quantum well(MQW) structure formed by a plurality of well layers and barrier layersdisposed alternately. The band gap of the well layer is lower than thatof the barrier layer so that electrons and holes are confined by eachwell layer of the MQW structure. Thus electrons and holes arerespectively injected from the n-type semiconductor layer and the p-typesemiconductor layer to be combined with each other in the well layersand photons are emitted.

The brightness of LED is determined by an internal quantum efficiencyand a light-extraction efficiency. The internal quantum efficiency (IQE)is the ratio of electron hole pairs involved in radiation recombinationto the injected electron hole pairs. The refractive index of air and GaNrespectively is 1 and 2.4. According to total internal reflectionequation, the critical angle of GaN LED that allows light to be emittedinto air is about 24 degrees. Thus the light-extraction rate is about4.34%. Due to total internal reflection of GaN and air, light emittingfrom LED is restricted inside the LED and the light-extraction rate isquite low. Thus many researches focus on improvement of thelight-extraction efficiency. For example, one of the methods is toperform surface treatments on a p-type GaN layer for reducing the totalinternal reflection and further improving the light-extractionefficiency. The surface treatment includes surface roughening andchanges of LED morphology. Another method is to separate the n-type GaNlayer from the substrate and a rough structure is formed over the n-typeGaN layer. Then the GaN semiconductor layer is attached to the substrateby glue for improving the light-extraction efficiency. However, thefirst method can only be used to treat an exposed p-type GaNsemiconductor layer on top of the LED chip. Thus the improvement of thelight-extraction efficiency has a certain limit. The process of thesecond method is quite complicated and the glue has a problem of poorheat dissipation. Therefore the light emitting efficiency of LEDproduced by the above two methods is unable to be increased effectively.

Moreover, the concentration of the dopant in the p-type GaN layer isunable to be increased effectively so that the resistance of the p-typeGaN layer is quite large. Thus current is unable to be spread evenly inthe p-type GaN layer when the current flows from metal electrodes to theGaN semiconductor layer. The uneven current spreading results in thatthe lighting area is confined under the metal electrodes (n-typeelectrode ad p-type electrode). The light emitting efficiency of LED isalso decreased significantly.

In order to overcome the above shortcomings of the nitride semiconductorstructure and the semiconductor light emitting device available now,there is a need to provide a novel nitride semiconductor structure and anew semiconductor light emitting device.

SUMMARY OF THE INVENTION

Therefore it is a primary object of the present invention to provide anitride semiconductor structure in which a second type dopedsemiconductor layer has a high concentration of a second type dopant(larger than 5×10¹⁹ cm⁻³) and a thickness that is smaller than 30 nm soas to improve the light-extraction efficiency.

It is another object of the present invention to provide a semiconductorlight emitting device including the above nitride semiconductorstructure for providing a good light emitting efficiency.

In order to achieve the above objects, a nitride semiconductor structuremainly includes a first type doped semiconductor layer, a second typedoped semiconductor layer, and a light emitting layer disposed betweenthe first type doped semiconductor layer and the second type dopedsemiconductor layer. The second type doped semiconductor layer is dopedwith a second type dopant (magnesium is preferred) at a concentrationlarger than 5×10¹⁹ cm⁻³ and having a thickness smaller than 30 nm. Thesecond type doped semiconductor layer is formed under relatively highpressure (larger than 300 torr).

Moreover, a hole supply layer is disposed between the light emittinglayer and the second type doped semiconductor layer. The hole supplylayer is made of Al_(x)In_(y)Ga_(1-x-y)N while x and y satisfy theconditions: 0<x<1, 0<y<1, and 0<x+y<1. The hole supply layer is dopedwith a second type dopant at a concentration larger than 10¹⁸ cm⁻³. Thehole supply layer is also doped with a Group IV-A element at aconcentration ranging from 10¹⁷ cm⁻³ to 10²⁰ cm⁻³ so that more holes areprovided to enter the light emitting layer and the electron-holerecombination is further increased. The light emitting layer has amultiple quantum well (MQW) structure. The band gap of the hole supplylayer is larger than that of the well layer of the MQW structure so thatholes in the hole supply layer can enter the well layer of the MQWstructure. Thus the electron-hole recombination rate is increased andthe light emitting efficiency is further improved.

As to the light emitting layer in the multiple quantum well (MQW)structure, the MQW structure includes a plurality of well layers andbarrier layers stacked alternately while there is one well layer betweenevery two barrier layers. The barrier layer is made ofAl_(x)In_(y)Ga_(1-x-y)N, wherein x and y satisfy the conditions: 0<x<1,0<y<1, and 0<x+y<1. The well layer is made of In_(z)Ga_(1-z)N (0<z<1).The thickness of the well layer is ranging from 3.5 nm to 7 nm and thebarrier layer is doped with a first type dopant at a concentrationranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³.

Furthermore, a second type carrier blocking layer made ofAl_(x)Ga_(1-x)N (0<x<1) is disposed between the hole supply layer andthe second type doped semiconductor layer while a first type carrierblocking layer made of Al_(x)Ga_(1-x)N (0<x<1) is disposed between thelight emitting layer and the first type doped semiconductor layer. Dueto the property that the band gap of AlGaN containing aluminum is largerthan the band gap of GaN, carriers are confined in the MQW structure andelectron-hole recombination rate is improved. Thus the light emittingefficiency is increased.

A semiconductor light emitting device of the present invention includesthe above nitride semiconductor structure disposed on a substrate, afirst type electrode and the second type electrode used together forproviding electric power. Due to smaller thickness of the second typedoped semiconductor layer, the second type electrode is getting closerto the surface of the light emitting layer. Thus a stronger coupling isgenerated due to resonance between photons from the light emitting layerand surface plasmon. Therefore the light emitting efficiency isimproved. Moreover, the second type doped semiconductor layer has ahigher concentration of the second type dopant than that of theconventional p-type GaN layer so that the resistance of the second typedoped semiconductor layer is lower. Thus even current spreading in thesecond type doped semiconductor layer is achieved when the current flowsfrom the second type electrode to the first type electrode. Thereforethe LED gets a better light emitting efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings, wherein

FIG. 1 is a schematic drawing showing a cross section of an embodimentof a nitride semiconductor structure according to the present invention;

FIG. 2 is a schematic drawing showing a cross section of an embodimentof a semiconductor light emitting device including a nitridesemiconductor structure according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following embodiments, when it is mentioned that a layer ofsomething or a structure is disposed over or under a substrate, anotherlayer of something, or another structure, that means the two structures,the layers of something, the layer of something and the substrate, orthe structure and the substrate can be directly or indirectly connected.The indirect connection means there is at least one intermediate layerdisposed therebetween.

Referring to FIG. 1, a cross section of an embodiment of nitridesemiconductor structure according to the present invention is revealed.The nitride semiconductor structure includes a first type dopedsemiconductor layer 3 and a second type doped semiconductor layer 7. Alight emitting layer 5 is disposed between the first type dopedsemiconductor layer 3 and the second type doped semiconductor layer 7.The second type doped semiconductor layer 7 is doped with a second typedopant at a concentration larger than 5×10¹⁹ cm⁻³ while a thickness ofthe second type doped semiconductor layer is smaller than 30 mm. Thesecond dopant can be magnesium or zinc while magnesium is preferred.

Moreover, the first type doped semiconductor layer 3 is made of Si-dopedor Ge-doped GaN based materials (n-type doped GaN based semiconductorlayer) and the second type doped semiconductor layer 7 is made ofMg-doped GaN based materials (p-type doped GaN based semiconductorlayer). The concentration of the Mg doped is larger than 5×10¹⁹ cm⁻³.The materials are not limited to the above ones. The first type dopedsemiconductor layer 3 and the second type doped semiconductor layer 7are produced by metalorganic chemical vapor deposition (MOCVD) while thesecond type doped semiconductor layer 7 is formed under relativelyhigher pressure (larger than 300 torr).

Furthermore, a hole supply layer 8 is disposed between the lightemitting layer 5 and the second type doped semiconductor layer 7. Thehole supply layer 8 is made of Al_(x)In_(y)Ga_(1-x-y)N (0<x<1, 0<y<1,0<x+y<1) and is doped with a second dopant (such as Mg or Zn) at aconcentration larger than 10¹⁸ cm⁻³. Besides the second dopant, the holesupply layer 8 is also doped with a Group IV-A element (carbon ispreferred) at a concentration ranging from 10¹⁷ to 10²⁰ cm⁻³. Thepentavalent nitrogen atom is replaced by carbon (Group IV-A) so thatthere is one more positively charged hole. Thus the hole supply layer 8has a higher concentration of holes and more holes are provided to enterthe light emitting layer 5. Therefore the electron-hole recombination isfurther increased. As to the light emitting layer 5, it has a multiplequantum well (MQW) structure. The band gap of the hole supply layer 8 islarger than that of a well layer 51 of the MQW structure so that holesin the hole supply layer 8 can enter the well layer 51 of the MQWstructure to increase the electron-hole recombination rate and furtherimprove the light emitting efficiency.

In addition, for reducing stress caused by lattice mismatch between thewell layer and the barrier layer of the MQW structure, the barrier layer52 of the MQW structure is made of quaternary Al_(x)In_(y)Ga_(1-x-y)Nwhile x and y satisfy the conditions: 0<x<1, 0<y<1, and 0<x+y<1. Thewell layer 51 is made of ternary In_(z)Ga_(1-z)N and 0<z<1. Due to theproperty that both quaternary AlGaInN barrier layers and ternary InGaNwell layers have the same element-indium, the quaternary composition canbe adjusted and improved for providing a lattice matching composition.Thus the barrier layers and the well layers have closer latticeconstant. The thickness of the well layer 51 is ranging from 3.5 nm to 7nm. The barrier layer 52 is doped with a first type dopant (such as Sior Ge) at a concentration ranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³ so as toreduce carrier screening effect and increase carrier-confinement.

The above nitride semiconductor structure further includes a second typecarrier blocking layer 6 disposed between the hole supply layer 8 andthe second type doped semiconductor layer 7, and a first type carrierblocking layer 4 disposed between the light emitting layer 5 and thefirst type doped semiconductor layer 3. The second type carrier blockinglayer 6 is made of Al_(x)Ga_(1-x)N (0<x<1) while the first type carrierblocking layer 4 is made of Al_(x)Ga_(1-x)N (0<x<1). Thereby carriersare confined in the MQW structure and the electron-hole recombinationrate is increased due to the property that the band gap of AlGaNcontaining aluminum is larger than the band gap of GaN. Therefore thelight emitting efficiency is increased.

The above nitride semiconductor structure is applied to semiconductorlight emitting devices. Referring to FIG. 2, a cross sectional view ofan embodiment of a semiconductor light emitting device is revealed. Thesemiconductor light emitting device at least includes: a substrate 1, afirst type doped semiconductor layer 3 disposed over the substrate 1 andmade of Si-doped or Ge-doped GaN based materials, a light emitting layer5 disposed over the first type doped semiconductor layer 3, a secondtype doped semiconductor layer 7 disposed over the light emitting layer5, a first type electrode 31 disposed on and in ohmic contact with thefirst type doped semiconductor layer 3, and a second type electrode 71disposed on and in ohmic contact with the second type dopedsemiconductor layer 7.

The materials for the substrate 1 include sapphire, silicon, SiC, ZnO,GaN, etc. The second type doped semiconductor layer 7 is doped with asecond type dopant at a concentration larger than 5×10¹⁹ cm⁻³ and havinga thickness smaller than 30 nm. The first type electrode 31 and thesecond type electrode 71 are used together to provide electric power andare made of (but not limited to) the following materials: titanium,aluminum, gold, chromium, nickel, platinum, and their alloys. Themanufacturing processes are well-known to people skilled in the art.

Moreover, a buffer layer 2 made of Al_(x)Ga_(1-x)N (0<x<1) is disposedbetween the substrate 1 and the first type doped semiconductor layer 3and is used for improving lattice constant mismatch between theheterogeneous substrate 1 and the first type doped semiconductor layer 3grown on the heterogeneous substrate 1. The buffer layer 2 is made ofGaN, InGaN, SiC, ZnO, etc.

When using the above semiconductor light emitting device, thelight-extraction efficiency is significantly improved and a better lightemitting efficiency is achieved because that the second type dopedsemiconductor layer 7 is doped with high-concentration Magnesium (higherthan 5×10¹⁹ cm⁻³) and is formed under relatively high pressure (largerthan 300 torr) with a thickness smaller than 30 nmm that is thinner thanconventional p-type GaN layer. The reasonable inference is that astronger coupling is generated due to photons from the light emittinglayer in resonance with surface plasmon when the second type electrodeis getting closer to the surface of the light emitting layer. Thus thelight emitting efficiency is increased. The surface plasmon resonancemeans free electrons fluctuations occurring on the surface of the secondtype electrode 71. Moreover, compared with the conventional p-type GaNlayer, the second type doped semiconductor layer 7 has a higherconcentration of the Mg dopant so that its resistance is relativelylower. Thus even current spreading is achieved when the current isflowing from the second type electrode 71 to the second type dopedsemiconductor layer 7. Therefore the light emitting diode gets a betterlight emitting efficiency.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A nitride semiconductor structure comprising: afirst type doped semiconductor layer, a second type doped semiconductorlayer, a light emitting layer disposed between the first type dopedsemiconductor layer and the second type doped semiconductor layer; ahole supply layer disposed between the light emitting layer and thesecond type doped semiconductor layer, wherein the hole supply layer ismade of Al_(x1)In_(y1)Ga_(1-x1-y1)N (0<x1<1, 0<y1<1, and 0<x1+y1<1)GaN-based semiconductor comprising Al and In; the hole supply layer isdoped with a second type dopant at a concentration larger than 10¹⁸cm⁻³; and a second type carrier blocking layer disposed between the holesupply layer and the second type doped semiconductor layer, wherein thesecond type carrier blocking layer is made of Al_(x2)Ga_(1-x2)N, wherein0<x2<1 GaN-based semiconductor comprising Al; wherein the second typedoped semiconductor layer is doped with the second type dopant at aconcentration larger than 5×10¹⁹ cm⁻³and a thickness of the second typedoped semiconductor layer is smaller than 30 nm.
 2. The nitridesemiconductor structure as claimed in claim 1, wherein the hole supplylayer is doped with a Group IV-A element at a concentration ranging from10¹⁷ cm⁻³ to 10²⁰ cm⁻³.
 3. The nitride semiconductor structure asclaimed in claim 1, wherein the light emitting layer has a multiplequantum well (MQW) structure and a band gap of the hole supply layer islarger than a band gap of a well layer of the MQW structure.
 4. Thenitride semiconductor structure as claimed in claim 1, wherein the lightemitting layer has a multiple quantum well (MQW) structure including aplurality well layers and barrier layers stacked alternately; one of thewell layers is disposed between every two barrier layers; the barrierlayer is made of Al_(x4)In_(y2)Ga_(1-x4-y2)N while x4 and y2 satisfy theconditions: 0<x4<1, 0<y2<1, and 0<x4+y2<1 GaN-based semiconductor; thewell layer is made of In_(z)Ga_(1-z)N (0<z<1) GaN-based semiconductorcomprising In.
 5. The nitride semiconductor structure as claimed inclaim 4, wherein a thickness of the well layer is ranging from 3.5 nm to7 mm.
 6. The nitride semiconductor structure as claimed in claim 4,wherein the barrier layer is doped with a first type dopant at aconcentration ranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³.
 7. The nitridesemiconductor structure as claimed in claim 1, wherein a first typecarrier blocking layer is disposed between the light emitting layer andthe first type doped semiconductor layer; the first type carrierblocking layer is made of Al_(x3)Ga_(1-x3)N, wherein 0<x3<1 GaN-basedsemiconductor comprising Al.
 8. A semiconductor light emitting devicecomprising: a substrate; a first type doped semiconductor layer disposedover the substrate; a first type carrier blocking layer disposed on thefirst type doped semiconductor layer, wherein the first type carrierblocking layer is made of Al_(x3)Ga_(1-x3)N, where 0<x3<1 GaN-basedsemiconductor comprising Al; a light emitting layer disposed over thefirst type doped semiconductor layer; a hole supply layer disposed onlight emitting layer, wherein the hole supply layer is made ofAl_(x1)In_(y1)Ga_(1-x1-y1)N where 0<x1<1, 0<y1<1, 0<x1+y1<1 GaN-basedsemiconductor comprising Al and In; a second type carrier blocking layerdisposed on the hole supply layer, wherein the second type carrierblocking layer is made of Al_(x2)Ga_(1-x2)N, wherein 0<x2<1 GaN-basedsemiconductor comprising Al; a second type doped semiconductor layerdisposed over the light emitting layer, doped with a second type dopantat a concentration larger than 5×10¹⁹ cm⁻³, and having a thicknesssmaller than 30 nm; a first type electrode disposed on and in ohmiccontact with the first type doped semiconductor layer,; and a secondtype electrode disposed on and in ohmic contact with the second typedoped semiconductor layer.
 9. The semiconductor light emitting device asclaimed in claim 8, wherein the hole supply layer is doped with a GroupIV-A element at a concentration ranging from 10¹⁷ cm⁻³ to 10²⁰ cm ⁻³.10. The semiconductor light emitting device as claimed in claim 8,wherein the light emitting layer has a multiple quantum well (MQW)structure and a band gap of the hole supply layer is larger than a bandgap of a well layer of the MQW structure.
 11. The semiconductor lightemitting device as claimed in claim 8, wherein the light emitting layerhas a multiple quantum well (MQW) structure including a plurality welllayers and barrier layers stacked alternately; one of the well layers isdisposed between every two barrier layers; the barrier layer is made ofAl_(x)In_(y2)Ga_(1-x4-y2)N while x4 and y2 satisfy the conditions:0<x4<1, 0<y2<1, and 0<x4+y2<1 GaN-based semiconductor; the well layer ismade of In_(z)Ga_(1-z)N (0<z<1) GaN-based semiconductor comprising In.12. The semiconductor light emitting device as claimed in claim 11,wherein a thickness of the well layer is ranging from 3.5 nm to 7 nm.13. The semiconductor light emitting device as claimed in claim 11,wherein the barrier layer is doped with a first type dopant at aconcentration ranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³.
 14. A nitridesemiconductor structure comprising: a first type doped semiconductorlayer, a second type doped semiconductor layer, a light emitting layerdisposed between the first type doped semiconductor layer and the secondtype doped semiconductor layer,; and a hole supply layer disposedbetween the light emitting layer and the second type doped semiconductorlayer,; wherein the second type doped semiconductor layer is doped witha second type dopant at a concentration larger than 5×10¹⁹ cm⁻³, athickness of the second type doped semiconductor layer is smaller than30 nm, and the hole supply layer is doped with a Group IV-A element. 15.The nitride semiconductor structure as claimed in claim 14, wherein thehole supply layer is made of Al_(x1)In_(y1)Ga_(1-x1-y1)N (0<x1<1,0<y1<1, and 0<x1+y1<1) GaN-based semiconductor comprising Al and In; thehole supply layer is doped with the second type dopant at aconcentration larger than 10¹⁸ cm⁻³.
 16. The nitride semiconductorstructure as claimed in claim 14, wherein the hole supply layer is dopedwith the Group IV-A element at a concentration ranging from 10¹⁷ cm⁻³ to10²⁰ cm⁻³.
 17. The nitride semiconductor structure as claimed in claim14, wherein the light emitting layer has a multiple quantum well (MQW)structure and a band gap of the hole supply layer is larger than a bandgap of a well layer of the MQW structure.
 18. The nitride semiconductorstructure as claimed in claim 14, wherein the light emitting layer has amultiple quantum well (MQW) structure including a plurality well layersand barrier layers stacked alternately; one of the well layers isdisposed between every two barrier layers; the barrier layer is made ofAl_(x4)In_(y2)Ga_(1-x4-y2)N while x4 and y2 satisfy the conditions:0<x4<1, 0<y2<1, and 0<x4+y2<1 GaN-based semiconductor; the well layer ismade of In_(z)Ga_(1-z)N (0<z<1) GaN-based semiconductor comprising In.19. The nitride semiconductor structure as claimed in claim 18, whereina thickness of the well layer is ranging from 3.5 nm to 7 nm.
 20. Thenitride semiconductor structure as claimed in claim 18, wherein thebarrier layer is doped with a first type dopant at a concentrationranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³.
 21. The nitride semiconductorstructure as claimed in claim 16 14, wherein a second type carrierblocking layer is disposed between the hole supply layer and the secondtype doped semiconductor layer; the second type carrier blocking layeris made of Al_(x2)Ga_(1-x2)N, wherein 0<x2<1 GaN-based semiconductorcomprising Al.
 22. The nitride semiconductor structure as claimed inclaim 14, wherein a first type carrier blocking layer is disposedbetween the light emitting layer and the first type doped semiconductorlayer, the first type carrier blocking layer is made ofAl_(x3)Ga_(1-x3)N, wherein 0<x3<1 GaN-based semiconductor comprising Al.23. A semiconductor light emitting device comprising: a substrate; afirst type doped semiconductor layer disposed over the substrate; alight emitting layer disposed over the first type doped semiconductorlayer; a second type doped semiconductor layer disposed over the lightemitting layer, doped with a second type dopant at a concentrationlarger than 5×10¹⁹ cm⁻³, and having a thickness smaller than 30 nm; ahole supply layer disposed between the light emitting layer and thesecond type doped semiconductor layer, wherein the hole supply layer isdoped with a Group IV-A element; a first type electrode disposed on andin ohmic contact with the first type doped semiconductor layer,; and asecond type electrode disposed on and in ohmic contact with the secondtype doped semiconductor layer.
 24. The nitride semiconductor structuresemiconductor light emitting device as claimed in claim 23, wherein thehole supply layer is made of Al_(x1)In_(y1)Ga_(1-x1-y1)N, wherein0<x1<1, 0<y1<1, and 0<x1+y1<1 GaN-based semiconductor comprising Al andIn.
 25. The nitride semiconductor structure semiconductor light emittingdevice as claimed in claim 23, wherein the hole supply layer is dopedwith the Group IV-A element at a concentration ranging from 10¹⁷ cm⁻³ to10²⁰ cm⁻³.
 26. The nitride semiconductor structure semiconductor lightemitting device as claimed in claim 23, wherein the light emitting layerhas a multiple quantum well (MQW) structure and a band gap of the holesupply layer is larger than a band gap of a well layer of the MQWstructure.
 27. The nitride semiconductor structure semiconductor lightemitting device as claimed in claim 23, wherein the light emitting layerhas a multiple quantum well (MQW) structure including a plurality welllayers and barrier layers stacked alternately; one of the well layers isdisposed between every two barrier layers; the barrier layer is made ofAl_(x4)In_(y2)Ga_(1-x4-y2)N while x4 and y2 satisfy the conditions:0<x4<1, 0<y2<1, and 0<x4+y2<1 GaN-based semiconductor; the well layer ismade of In_(z)Ga_(1-z)N, where 0<z<1 GaN-based semiconductor comprisingIn.
 28. The nitride semiconductor structure semiconductor light emittingdevice as claimed in claim 27, wherein a thickness of the well layer isranging from 3.5 nm to 7 nm.
 29. The nitride semiconductor structuresemiconductor light emitting device as claimed in claim 27, wherein thebarrier layer is doped with a first type dopant at a concentrationranging from 10¹⁶ cm⁻³ to 10¹⁸ cm⁻³.
 30. The nitride semiconductorstructure semiconductor light emitting device as claimed in claim 23,wherein a second type carrier blocking layer is disposed between thehole supply layer and the second type doped semiconductor layer; thesecond type carrier blocking layer is made of Al_(x2)Ga_(1-x2)N, wherein0<x2<1 GaN-based semiconductor comprising Al.
 31. The nitridesemiconductor structure semiconductor light emitting device as claimedin claim 23, wherein a first type carrier blocking layer is disposedbetween the light emitting layer and the first type doped semiconductorlayer, the first type carrier blocking layer is made ofAl_(x3)Ga_(1-x3)N, wherein 0<x3<1 GaN-based semiconductor comprising Al.